1. Field of the Invention
The present invention relates to an apparatus for identifying a user by comparing a facial image of the user which is captured by a camera with facial image information which has been stored in advance.
2. Description of the Related Art
When a computer system or a robot system is used today by a plurality of users, each of the users may be required to be identified for authentication. Attention has been directed to a technique for identifying users based on facial image information. According to the technique, facial image information of certain users is preregistered in a facial image identifying apparatus, and when a user is to be identified, a facial image of the user is captured by a CCD camera, for example, and the captured facial image is checked against the preregistered facial image information to determine whether the user to be identified has been registered or not.
One conventional apparatus based on the facial image identifying technology is a robot apparatus disclosed in Japanese laid-open patent publication No. 2000-222576, for example.
FIG. 1 of the accompanying drawings is a block diagram of a conventional basic facial image identifying apparatus, and FIG. 2 of the accompanying drawings is a flowchart of an operation sequence of the conventional basic facial image identifying apparatus shown in FIG. 1.
As shown in FIG. 1, conventional basic facial image identifying apparatus 300 comprises image capturing means 301, person detecting means 302, person identifying means 303, and information presenting means 304.
Image capturing means 301 comprises a CCD camera, for example, for capturing an image including a user's face and a surrounding background. Person detecting means 302 detects a facial image from the image captured by image capturing means 301. Person identifying means 303, which has stored facial image information of preregistered users (hereinafter referred to as “registered users”), checks the facial image detected by person detecting means 302 against the stored facial image information, and identifies the user who has produced the detected facial image. The term “identifies” refers to a process of determining whether the user who has produced the detected facial image is a registered user or not. Information presenting means 304 presents the identified result from person identifying means 303 to the user.
A basic detecting and identifying process carried out by facial image identifying apparatus 300 will be described below with reference to FIG. 2.
Image capturing means 301 captures an image, and person detecting means 302 detects a user's facial image from the captured image. Person identifying means 303 checks the facial image against facial image information of registered users. In step 401, person identifying means 303 determines whether the facial image detected by person detecting means 302 is the facial image of a registered user or not. If the user is a registered user, then person identifying means 303 determines which one of the registered users the user is. If the detected facial image is not the facial image of a registered user, then the detecting and identifying process starts to be carried out again. If the detected facial image is the facial image of a registered user, then information presenting means 304 presents the identified result including information representative of the registered user to the user in step 402.
When images are captured in general home interior environments, it is difficult to keep image capturing conditions such as lighting conditions constant at all times. Therefore, it is highly likely to encounter different image capturing conditions when facial image information of registered users is captured and when a facial image of a user to be identified is captured.
For identifying a user, facial image identifying apparatus 300 simply checks the captured facial image of the user against the stored facial image information of registered users. With such a simple checking process, it is difficult for facial image identifying apparatus 300 to produce good identified results at all times in spite of different image capturing conditions.
Japanese laid-open patent publication No. 2000-306095 discloses a facial image checking and retrieving system as another conventional apparatus based on the facial image identifying technology.
The disclosed facial image checking and retrieving system operates as follows: When the facial image checking and retrieving system acquires a new facial image of a person, it estimates environment parameters and object state parameters of the acquired facial image. Then, the facial image checking and retrieving system adjusts parameters of stored facial image information to process images thereof so as to be closer to the acquired new facial image, thereby generating facial images to be checked against. Thereafter, the facial image checking and retrieving system checks the acquired new facial image against those generated facial images for identifying the person.
The detecting and identifying process carried out by the robot apparatus disclosed in Japanese laid-open patent publication No. 2000-222576 and the facial image checking and retrieving system disclosed in Japanese laid-open patent publication No. 2000-306095 suffer the following common problems:
Facial image information stored in the person identifying means and new captured facial images have to represent user's faces correctly. However, when the robot apparatus or the facial image checking and retrieving system is used in actual room interior environments or used by a plurality of users, user's facial images may not be acquired correctly. In particular, if a user to be identified does not know how to use the robot apparatus or the facial image checking and retrieving system properly, then it is impossible to provide desirable situations suitable for capturing a facial image, and hence a user's facial image cannot easily be identified.
The facial image checking and retrieving system disclosed in Japanese laid-open patent publication No. 2000-306095 also has the following drawbacks:
For the purpose of adjusting parameters of stored facial image information to process images thereof, the stored facial image information needs to be of sufficiently high quality. However, it is difficult to capture high-quality facial image information in room interior environments, for example.
If parameters of a new captured facial image exceed an adjustable range for the parameters of the stored facial image information, then those parameters cannot sufficiently be adjusted. As a consequence, the facial image checking and retrieving system fails to produce highly accurate identified results.